This project will investigate the development of infants' detection of two kinds of temporal structure in audio-visual events: 1) temporal synchrony information; the coincidence between sights and sounds of impact, and 2) temporal pattern at each impact specifying the composition of an object; whether it is of a continuous or discontinuous substance. Infants of 4 different age groups, 2, 3 1/2, 5, and 7 1/2 months, will be tested. They will be shown films of two different kinds of objects in motion, along with the soundtrack to one of them, according to Spelke's visual preference and search method. One experiment will test detection of synchrony information while controlling for composition information; the other will test detection of composition information while controlling for synchrony. It is expected that infants will 1) improve with age in detection of both kinds of temporal structure, 2) detect temporal synchrony at an earlier age then composition information, and 3) develop intermodal knowledge or expectations about the events on the basis of detecting their temporal structure. This research will test a set of predictions regarding the order of appearance of intermodal capabilities, as derived from a Gibsonian differentiation model.